Plain English Meaning
A tiny pouch in your inner ear that senses when your head tilts or moves sideways. It uses small crystals sitting on hair-like sensors so your brain knows which way is up and whether you're speeding up or slowing down level with the ground.
Full Definition
A small fluid-filled sac in the vestibular system of the inner ear that detects horizontal linear acceleration and the head's orientation relative to gravity. It contains hair cells topped with a gelatinous layer holding tiny calcium carbonate crystals (otoliths), which shift with movement and gravity to stimulate the hair cells and send position signals to the brain.
Context Anchor
Seen in discussions of the ear, balance, and spatial disorientation during .